Hi Nick, looks like a fun project. If you could share your zone and general area, you might get more feedback.

I live in Sacramento, CA

Japanese maples usually like some protection from hot, direct sun, so check with your nursery to make sure it's safe to put one in that open area. I'd give the bed a more defined shape, maybe a longer shape with some curve. Then add some evergreen foundation plantings on the ends/in the back along the wall to be your "bones." then some colorful perennials in the middle, using complementary colors, textures and shapes, and then y ou could add border plants or annuals in the very front. Diana's Designs

Nick, I noticed there are a few Japanese style gardens in your area so they might be a good resource for lighting upon cultivars that will do well. Houzz also has some good articles on achieving the zen look you are after.

The only way I can have Japanese maples - I live just outside of Sacramento- is with the protection of other shade trees/structures. The summer days can be brutal for them. I would suggest visiting Capital Nursery or Green Acres Nursery for growing advise in our zone 9 area.

Yes it is imperative you get the right planting material for your zone. IMO a zen garden does no include regular lawn grass so I think if you want this idea prepare to have it make up the whole front yard. With boulders, sand ,moss type ground cover tall grasses and plants that work in your zone. It might become an interesting combo of Zen and xeriscape garden which could be interesting. There types of Japanese maples that might work in your zone.